Reference: https://src.fedoraproject.org/rpms/dhcp/blob/rawhide/f/0012-RFC-3442-Classless-Static-Route-Option-for-DHCPv4-51.patch
From 7e6299e72feaaf7e8bd499614999ba8a07dd1a8a Mon Sep 17 00:00:00 2001
From: Pavel Zhukov <pzhukov@redhat.com>
Date: Thu, 21 Feb 2019 10:32:35 +0100
Subject: [PATCH 12/28] RFC 3442 - Classless Static Route Option for DHCPv4
 (#516325)

(Submitted to dhcp-bugs@isc.org - [ISC-Bugs #24572])
---
 client/clparse.c      | 13 ++++++++--
 common/dhcp-options.5 | 43 +++++++++++++++++++++++++++++++++
 common/inet.c         | 54 +++++++++++++++++++++++++++++++++++++++++
 common/options.c      | 49 ++++++++++++++++++++++++++++++++++++-
 common/parse.c        | 56 ++++++++++++++++++++++++++++++++++++++++++-
 common/tables.c       |  2 ++
 includes/dhcp.h       |  1 +
 includes/dhcpd.h      |  2 ++
 includes/dhctoken.h   |  3 ++-
 9 files changed, 218 insertions(+), 5 deletions(-)

diff --git a/client/clparse.c b/client/clparse.c
index 902b523..57f6456 100644
--- a/client/clparse.c
+++ b/client/clparse.c
@@ -31,7 +31,7 @@
 
 struct client_config top_level_config;
 
-#define NUM_DEFAULT_REQUESTED_OPTS	14
+#define NUM_DEFAULT_REQUESTED_OPTS	15
 /* There can be 2 extra requested options for DHCPv4-over-DHCPv6. */
 struct option *default_requested_options[NUM_DEFAULT_REQUESTED_OPTS + 2 + 1];
 
@@ -90,7 +90,11 @@ isc_result_t read_client_conf ()
 				dhcp_universe.code_hash, &code, 0, MDL);
 
 	/* 4 */
-	code = DHO_ROUTERS;
+	/* The Classless Static Routes option code MUST appear in the parameter
+     * request list prior to both the Router option code and the Static
+     * Routes option code, if present. (RFC3442)
+	 */
+	code = DHO_CLASSLESS_STATIC_ROUTES;
 	option_code_hash_lookup(&default_requested_options[3],
 				dhcp_universe.code_hash, &code, 0, MDL);
 
@@ -144,6 +148,11 @@ isc_result_t read_client_conf ()
 	option_code_hash_lookup(&default_requested_options[13],
 				dhcp_universe.code_hash, &code, 0, MDL);
 
+	/* 15 */
+	code = DHO_ROUTERS;
+	option_code_hash_lookup(&default_requested_options[14],
+				dhcp_universe.code_hash, &code, 0, MDL);
+
 	for (code = 0 ; code < NUM_DEFAULT_REQUESTED_OPTS ; code++) {
 		if (default_requested_options[code] == NULL)
 			log_fatal("Unable to find option definition for "
diff --git a/common/dhcp-options.5 b/common/dhcp-options.5
index a784b32..86f04ed 100644
--- a/common/dhcp-options.5
+++ b/common/dhcp-options.5
@@ -117,6 +117,26 @@ hexadecimal, separated by colons.  For example:
 or
   option dhcp-client-identifier 43:4c:49:45:54:2d:46:4f:4f;
 .fi
+.PP
+The
+.B destination-descriptor
+describe the IP subnet number and subnet mask
+of a particular destination using a compact encoding. This encoding
+consists of one octet describing the width of the subnet mask,
+followed by all the significant octets of the subnet number.
+The following table contains some examples of how various subnet
+number/mask combinations can be encoded:
+.nf
+.sp 1
+Subnet number   Subnet mask      Destination descriptor
+0               0                0
+10.0.0.0        255.0.0.0        8.10
+10.0.0.0        255.255.255.0    24.10.0.0
+10.17.0.0       255.255.0.0      16.10.17
+10.27.129.0     255.255.255.0    24.10.27.129
+10.229.0.128    255.255.255.128  25.10.229.0.128
+10.198.122.47   255.255.255.255  32.10.198.122.47
+.fi
 .SH SETTING OPTION VALUES USING EXPRESSIONS
 Sometimes it's helpful to be able to set the value of a DHCP option
 based on some value that the client has sent.  To do this, you can
@@ -1093,6 +1113,29 @@ dhclient-script will create routes:
 .RE
 .PP
 .nf
+.B option \fBclassless-static-routes\fR \fIdestination-descriptor ip-address\fR
+                            [\fB,\fR \fIdestination-descriptor ip-address\fR...]\fB;\fR
+.fi
+.RS 0.25i
+.PP
+This option (see RFC3442) specifies a list of classless static routes
+that the client should install in its routing cache.
+.PP
+This option can contain one or more static routes, each of which
+consists of a destination descriptor and the IP address of the router
+that should be used to reach that destination.
+.PP
+Many clients may not implement the Classless Static Routes option.
+DHCP server administrators should therefore configure their DHCP
+servers to send both a Router option and a Classless Static Routes
+option, and should specify the default router(s) both in the Router
+option and in the Classless Static Routes option.
+.PP
+If the DHCP server returns both a Classless Static Routes option and
+a Router option, the DHCP client ignores the Router option.
+.RE
+.PP
+.nf
 .B option \fBstreettalk-directory-assistance-server\fR \fIip-address\fR
                                            [\fB,\fR \fIip-address\fR...]\fB;\fR
 .fi
diff --git a/common/inet.c b/common/inet.c
index 0f7f168..7c446d4 100644
--- a/common/inet.c
+++ b/common/inet.c
@@ -519,6 +519,60 @@ free_iaddrcidrnetlist(struct iaddrcidrnetlist **result) {
 	return ISC_R_SUCCESS;
 }
 
+static const char *
+inet_ntopdd(const unsigned char *src, unsigned srclen, char *dst, size_t size)
+{
+	char tmp[sizeof("32.255.255.255.255")];
+	int len;
+
+	switch (srclen) {
+		case 2:
+			len = sprintf (tmp, "%u.%u", src[0], src[1]);
+			break;
+		case 3:
+			len = sprintf (tmp, "%u.%u.%u", src[0], src[1], src[2]);
+			break;
+		case 4:
+			len = sprintf (tmp, "%u.%u.%u.%u", src[0], src[1], src[2], src[3]);
+			break;
+		case 5:
+			len = sprintf (tmp, "%u.%u.%u.%u.%u", src[0], src[1], src[2], src[3], src[4]);
+			break;
+		default:
+			return NULL;
+	}
+	if (len < 0)
+		return NULL;
+
+	if (len > size) {
+		errno = ENOSPC;
+		return NULL;
+	}
+
+	return strcpy (dst, tmp);
+}
+
+/* pdestdesc() turns an iaddr structure into a printable dest. descriptor */
+const char *
+pdestdesc(const struct iaddr addr) {
+	static char pbuf[sizeof("255.255.255.255.255")];
+
+	if (addr.len == 0) {
+		return "<null destination descriptor>";
+	}
+	if (addr.len == 1) {
+		return "0";
+	}
+	if ((addr.len >= 2) && (addr.len <= 5)) {
+		return inet_ntopdd(addr.iabuf, addr.len, pbuf, sizeof(pbuf));
+	}
+
+	log_fatal("pdestdesc():%s:%d: Invalid destination descriptor length %d.",
+		  MDL, addr.len);
+	/* quell compiler warnings */
+	return NULL;
+}
+
 /* piaddr() turns an iaddr structure into a printable address. */
 /* XXX: should use a const pointer rather than passing the structure */
 const char *
diff --git a/common/options.c b/common/options.c
index 92c8fee..66433c4 100644
--- a/common/options.c
+++ b/common/options.c
@@ -734,7 +734,11 @@ cons_options(struct packet *inpacket, struct dhcp_packet *outpacket,
 		 * packet.
 		 */
 		priority_list[priority_len++] = DHO_SUBNET_MASK;
-		priority_list[priority_len++] = DHO_ROUTERS;
+		if (lookup_option(&dhcp_universe, cfg_options,
+							DHO_CLASSLESS_STATIC_ROUTES))
+			priority_list[priority_len++] = DHO_CLASSLESS_STATIC_ROUTES;
+		else
+			priority_list[priority_len++] = DHO_ROUTERS;
 		priority_list[priority_len++] = DHO_DOMAIN_NAME_SERVERS;
 		priority_list[priority_len++] = DHO_HOST_NAME;
 		priority_list[priority_len++] = DHO_FQDN;
@@ -1812,6 +1816,7 @@ const char *pretty_print_option (option, data, len, emit_commas, emit_quotes)
 	unsigned long tval;
 	isc_boolean_t a_array = ISC_FALSE;
 	int len_used;
+	unsigned int octets = 0;
 
 	if (emit_commas)
 		comma = ',';
@@ -1820,6 +1825,7 @@ const char *pretty_print_option (option, data, len, emit_commas, emit_quotes)
 
 	memset (enumbuf, 0, sizeof enumbuf);
 
+	if (option->format[0] != 'R') { /* see explanation lower */
 	/* Figure out the size of the data. */
 	for (l = i = 0; option -> format [i]; i++, l++) {
 		if (l >= sizeof(fmtbuf) - 1)
@@ -2029,6 +2035,33 @@ const char *pretty_print_option (option, data, len, emit_commas, emit_quotes)
 	if (numhunk < 0)
 		numhunk = 1;
 
+	} else { /* option->format[i] == 'R') */
+		/* R (destination descriptor) has variable length.
+		 * We can find it only in classless static route option,
+		 * so we are for sure parsing classless static route option now.
+		 * We go through whole the option to check whether there are no
+		 * missing/extra bytes.
+		 * I didn't find out how to improve the existing code and that's the
+		 * reason for this separate 'else' where I do my own checkings.
+		 * I know it's little bit unsystematic, but it works.
+		 */
+		numhunk = 0;
+		numelem = 2; /* RI */
+		fmtbuf[0]='R'; fmtbuf[1]='I'; fmtbuf[2]=0;
+		for (i =0; i < len; i = i + octets + 5) {
+			if (data[i] > 32) { /* subnet mask width */
+				log_error ("wrong subnet mask width in destination descriptor");
+				break;
+			}
+			numhunk++;
+			octets = ((data[i]+7) / 8);
+		}
+		if (i != len) {
+			log_error ("classless static routes option has wrong size or "
+					   "there's some garbage in format");
+		}
+	}
+
 	/* Cycle through the array (or hunk) printing the data. */
 	for (i = 0; i < numhunk; i++) {
 		if ((a_array == ISC_TRUE) && (i != 0) && (numelem > 0)) {
@@ -2197,6 +2230,20 @@ const char *pretty_print_option (option, data, len, emit_commas, emit_quotes)
 				strcpy(op, piaddr(iaddr));
 				dp += 4;
 				break;
+
+			      case 'R':
+				if (dp[0] <= 32)
+					iaddr.len = (((dp[0]+7)/8)+1);
+				else {
+					log_error ("wrong subnet mask width in destination descriptor");
+					return "<error>";
+				}
+
+				memcpy(iaddr.iabuf, dp, iaddr.len);
+				strcpy(op, pdestdesc(iaddr));
+				dp += iaddr.len;
+				break;
+
 			      case '6':
 				iaddr.len = 16;
 				memcpy(iaddr.iabuf, dp, 16);
diff --git a/common/parse.c b/common/parse.c
index b123a6c..7cf4f2a 100644
--- a/common/parse.c
+++ b/common/parse.c
@@ -344,6 +344,39 @@ int parse_ip_addr (cfile, addr)
 	return 0;
 }
 
+/*
+ * destination-descriptor :== NUMBER DOT NUMBER |
+ *                            NUMBER DOT NUMBER DOT NUMBER |
+ *                            NUMBER DOT NUMBER DOT NUMBER DOT NUMBER |
+ *                            NUMBER DOT NUMBER DOT NUMBER DOT NUMBER DOT NUMBER
+ */
+
+int parse_destination_descriptor (cfile, addr)
+	struct parse *cfile;
+	struct iaddr *addr;
+{
+		unsigned int mask_width, dest_dest_len;
+		addr -> len = 0;
+		if (parse_numeric_aggregate (cfile, addr -> iabuf,
+									 &addr -> len, DOT, 10, 8)) {
+			mask_width = (unsigned int)addr->iabuf[0];
+			dest_dest_len = (((mask_width+7)/8)+1);
+			if (mask_width > 32) {
+				parse_warn (cfile,
+				"subnet mask width (%u) greater than 32.", mask_width);
+			}
+			else if (dest_dest_len != addr->len) {
+				parse_warn (cfile,
+				"destination descriptor with subnet mask width %u "
+				"should have %u octets, but has %u octets.",
+				mask_width, dest_dest_len, addr->len);
+			}
+
+			return 1;
+		}
+		return 0;
+}
+
 /*
  * Return true if every character in the string is hexadecimal.
  */
@@ -724,8 +757,10 @@ unsigned char *parse_numeric_aggregate (cfile, buf,
 		if (count) {
 			token = peek_token (&val, (unsigned *)0, cfile);
 			if (token != separator) {
-				if (!*max)
+				if (!*max) {
+					*max = count;
 					break;
+				}
 				if (token != RBRACE && token != LBRACE)
 					token = next_token (&val,
 							    (unsigned *)0,
@@ -1672,6 +1707,9 @@ int parse_option_code_definition (cfile, option)
 	      case IP_ADDRESS:
 		type = 'I';
 		break;
+	      case DESTINATION_DESCRIPTOR:
+		type = 'R';
+		break;
 	      case IP6_ADDRESS:
 		type = '6';
 		break;
@@ -5124,6 +5162,15 @@ int parse_option_token (rv, cfile, fmt, expr, uniform, lookups)
 		}
 		break;
 
+	      case 'R': /* destination descriptor */
+		if (!parse_destination_descriptor (cfile, &addr)) {
+			return 0;
+		}
+		if (!make_const_data (&t, addr.iabuf, addr.len, 0, 1, MDL)) {
+			return 0;
+		}
+		break;
+
 	      case '6': /* IPv6 address. */
 		if (!parse_ip6_addr(cfile, &addr)) {
 			return 0;
@@ -5401,6 +5448,13 @@ int parse_option_decl (oc, cfile)
 					goto exit;
 				len = ip_addr.len;
 				dp = ip_addr.iabuf;
+				goto alloc;
+
+			      case 'R': /* destination descriptor */
+				if (!parse_destination_descriptor (cfile, &ip_addr))
+					goto exit;
+				len = ip_addr.len;
+				dp = ip_addr.iabuf;
 
 			      alloc:
 				if (hunkix + len > sizeof hunkbuf) {
diff --git a/common/tables.c b/common/tables.c
index ce12fcd..96521a6 100644
--- a/common/tables.c
+++ b/common/tables.c
@@ -45,6 +45,7 @@ HASH_FUNCTIONS (option_code, const unsigned *, struct option,
    Format codes:
 
    I - IPv4 address
+   R - destination descriptor (RFC3442)
    6 - IPv6 address
    l - 32-bit signed integer
    L - 32-bit unsigned integer
@@ -223,6 +224,7 @@ static struct option dhcp_options[] = {
 #endif
 	{ "subnet-selection", "I",		&dhcp_universe, 118, 1 },
 	{ "domain-search", "D",			&dhcp_universe, 119, 1 },
+	{ "classless-static-routes", "RIA",	&dhcp_universe, 121, 1 },
 	{ "vivco", "Evendor-class.",		&dhcp_universe, 124, 1 },
 	{ "vivso", "Evendor.",			&dhcp_universe, 125, 1 },
 #if 0
diff --git a/includes/dhcp.h b/includes/dhcp.h
index cafe172..5a73129 100644
--- a/includes/dhcp.h
+++ b/includes/dhcp.h
@@ -159,6 +159,7 @@ struct dhcp_packet {
 #define DHO_V6_ONLY_PREFERRED			108 /* RFC8925 */
 #define DHO_SUBNET_SELECTION			118 /* RFC3011! */
 #define DHO_DOMAIN_SEARCH			119 /* RFC3397 */
+#define DHO_CLASSLESS_STATIC_ROUTES		121 /* RFC3442 */
 #define DHO_VIVCO_SUBOPTIONS			124
 #define DHO_VIVSO_SUBOPTIONS			125
 
diff --git a/includes/dhcpd.h b/includes/dhcpd.h
index 4a57002..25e1c72 100644
--- a/includes/dhcpd.h
+++ b/includes/dhcpd.h
@@ -2967,6 +2967,7 @@ isc_result_t range2cidr(struct iaddrcidrnetlist **result,
 			const struct iaddr *lo, const struct iaddr *hi);
 isc_result_t free_iaddrcidrnetlist(struct iaddrcidrnetlist **result);
 const char *piaddr (struct iaddr);
+const char *pdestdesc (struct iaddr);
 char *piaddrmask(struct iaddr *, struct iaddr *);
 char *piaddrcidr(const struct iaddr *, unsigned int);
 u_int16_t validate_port(char *);
@@ -3189,6 +3190,7 @@ void parse_client_lease_declaration (struct parse *,
 int parse_option_decl (struct option_cache **, struct parse *);
 void parse_string_list (struct parse *, struct string_list **, int);
 int parse_ip_addr (struct parse *, struct iaddr *);
+int parse_destination_descriptor (struct parse *, struct iaddr *);
 int parse_ip_addr_with_subnet(struct parse *, struct iaddrmatch *);
 void parse_reject_statement (struct parse *, struct client_config *);
 
diff --git a/includes/dhctoken.h b/includes/dhctoken.h
index 6daa422..3f5334e 100644
--- a/includes/dhctoken.h
+++ b/includes/dhctoken.h
@@ -378,7 +378,8 @@ enum dhcp_token {
 	TOKEN_OCTAL = 678,
 	KEY_ALGORITHM = 679,
 	BOOTP_BROADCAST_ALWAYS = 680,
-	DISCONNECT = 681
+	DESTINATION_DESCRIPTOR = 681,
+	DISCONNECT = 682
 };
 
 #define is_identifier(x)	((x) >= FIRST_TOKEN &&	\
-- 
2.35.1